Thanks Scully. That was a great video too.Stirring up substrate can cause an ammonia spike, too much ammonia can negitively impact plants. Try testing that.
If you didn't clean your dragon stone throroughly enough it may have some clay deposits in it that are effecting your parameters. It would basically be like adding a bunch of organics/soil to your tank. Also there are types of dragon stone that aren't really dragon stone, they can affect your parameters.